Recently, in order to improve the accuracy of forming a tire, a method for forming a tire by the use of a rigid core (hereinafter sometimes referred to as core method) has been proposed (see Patent Documents 1 and 2, for example). The rigid core has a core main body having a outer shape according with a shape of the inner surface of a vulcanized tire. A raw tire is formed by sequentially applying tire components onto the core main body. And the raw tire is, together with the rigid core, put into a vulcanizing mold to be sandwiched between the core main body as the inner die and the vulcanizing mold as the outer die, and the raw tire is vulcanization molded.
As shown in FIG. 8 (A), the core main body (a) is composed of a plurality of core segments (c) which are divided in the circumferential direction. Thus, after the tire is vulcanized, the core main body (a) is disassembled and removed. Each of the core segments (c) has mating faces (cs) in both end surfaces in the circumferential direction. The mating faces (cs) of each core segment (c) are butted to circumferentially adjacent mating faces, and thereby the core main body (a) is formed in an annular shape.
Here, the temperature of the core main body (a) is changed from normal temperature (about 15 to 50 degrees C.) during forming the raw tire to high temperature (100 degrees C. or more) during vulcanization. Accordingly, as enlargedly shown in FIG. 8 (B), the core main body (a) at the normal temperature is provided between the mating faces (cs, cs) with a gap (d) of about 0.2 mm, for example. As a result, in the thermal expansion state during vulcanization, the mating faces (cs) substantially contact with each other.
In the core method, the vulcanizing mold is closed and the internal pressure is added before the core main body (a) expands thermally. Therefore, an phenomenon that part of the rubber (g) of the raw tire T penetrates into the gap (d), so-called rubber bite phenomenon, occurs. As shown enlargedly in FIG. 8 (C), by the decrease in the gap (d) due to the thermal expansion, the rubber (g) penetrating into the gap (d) is extend as a thin membrane-like mold flash g1 and adhered to the mating faces (cs). As a result, at each time the tire is vulcanization molded, it is necessary to remove the membrane-like mold flash g1 from the mating faces (cs) of the disassembled core segments (c). Therefore, there is a problem such that the production efficiency of the tire is reduced.